Cydonia was first imaged in detail by the Viking 1 and Viking 2 orbiters. Eighteen images of the Cydonia region were taken by the orbiters, of which seven have resolutions better than 250 m/pixel (820 ft/pixel). The other eleven images have resolutions that are worse than 550 m/pixel (1800 ft/pixel) and are of limited use for studying surface features. Of the seven good images, the lighting and time at which two pairs of images were taken are so close as to reduce the number to five distinct images. The Mission to Mars: Viking Orbiter Images of Mars CD-ROM set image numbers for these are: 035A72 (VO-1010), 070A13 (VO-1011), 561A25 (VO-1021), 673B54 & 673B56 (VO-1063), and 753A33 & 753A34 (VO-1028).[11][12]

In one of the images taken by Viking 1 on July 25, 1976, a two-kilometre-long (1.2 mi) Cydonian mesa, situated at 40.75° north latitude and 9.46° west longitude,[13] had the appearance of a humanoid face. When the image was originally acquired, Viking chief scientist Gerry Soffen dismissed the "Face on Mars" in image 035A72[14] as a "trick of light and shadow".[15][16] However, a second image, 070A13, also shows the "face", and was acquired 35 Viking orbits later at a different sun-angle from the 035A72 image. This latter discovery was made independently by Vincent DiPietro and Gregory Molenaar, two computer engineers at NASA's Goddard Space Flight Center. DiPietro and Molenaar discovered the two misfiled images, Viking frames 035A72 and 070A13, while searching through NASA archives.[17]

More than 20 years after the Viking 1 images were taken, a succession of spacecraft visited Mars and made new observations of the Cydonia region. These spacecraft have included NASA's Mars Global Surveyor (1997–2006) and Mars Reconnaissance Orbiter (2006–),[18] and the European Space Agency's Mars Express probe (2003–).[19] In contrast to the relatively low resolution of the Viking images of Cydonia, these new platforms afford much improved resolution. For instance, the Mars Express images are at a resolution of 14 m/pixel (46 ft/pixel) or better. By combining data from the High Resolution Stereo Camera (HRSC) on the Mars Express probe and the Mars Orbiter Camera (MOC) on board NASA's Mars Global Surveyor it has been possible to create a three-dimensional representation of the "Face on Mars".[20]

While accepting the "face" as a subject for scientific study, astronomer Carl Sagan criticized much of the speculation concerning it in the chapter "The Man in the Moon and the Face on Mars" in his book The Demon-Haunted World.[33][34] The "face" is also a common topic among skeptics groups, who use it as an example of credulity.[35] They point out that there are other faces on Mars but these do not elicit the same level of study. One example is the Galle Crater, which takes the form of a smiley, while others resemble Kermit the Frog or other celebrities.[36] On this latter similarity, Discover magazine's "Skeptical Eye" column ridiculed Hoagland's claims, asking if he believed the aliens were fans of Sesame Street.[17][37]

In 1958, almost two decades prior to the first images of the Face from the Viking probes, the comic book artistJack Kirby wrote a story entitled "The Face on Mars" for Harvey Comics (Race for the Moon Number 2, September 1958), in which a large face (oriented vertically rather than horizontally) served as a monument to an extinct humanoid race from Mars.[38][39]